There is considerable demand for the testing of species using electrochemical methods. These species include but are not limited to metals, glucose, biochemical species, gases and other redox species. Analysis of these species may be achieved at conventional large electrodes or at microelectrodes. The latter offer improved precision, sensitivity, improved signal to noise ratios, reduced interference from interfering species such as oxygen, and in addition the potential to measure species in highly resistive media. Therefore a considerable effort has been expended on methods to produce these electrodes in a well-defined microelectrode array format that retains all the advantages of single microelectrodes and provides higher currents compared to those obtainable at individual microelectrodes (pA-nA).
Existing methods of fabrication for these electrodes are either by hand using epoxy resin encapsulation (W. L. Caudill et al, Anal. Chem. (1982) 54:2532) which is too time consuming and inefficient, or require expensive equipment, as in the case of fabrication by photo-ablation with lasers (WO-A-9108474) and electron beam etching techniques (M. S. Wrighton, Science (1986) 231:32). Other methods such as fabrication by the adhesion of microporous membranes (J. Wang and J. M. Zadeii, J. Electroanal. Chem. (1988) 249:339) failed due to heterogeneity in the arrangement of the pores resulting in poor reproducibility. J.Osteryoung and T. Hempel, J. Electrochem. Soc. (1986) 133:757, have investigated the use of thin film techniques but these have failed due to adhesion problems between the layers.
An object behind the present invention is to produce a satisfactory microelectrode array at low cost.